How can we add to the rendered object name his material name?

Question

Thanks to @FFeller, how helped me to automate a rendering of an object with the associated list of material. And Thanks to @Marty Fouts, how helped me with a script for renaming a rendered images with there associated materials. It works perfectly if the generated names are made by default. – link bellow – But I have many objects to render with the specific names, generated by a Compositing Output file, and the script looks for names like – 0000.png – and didn’t recognize names like – CUBE_ONE_0000.png – Knowing that I have a small knowledge of Python, can you please @Marty Fouts, help me to adjust the scripts. Images to illustrate my needs, hoping that I made it clear😊 Thanks a lot.

How can I render an object in a different material, each one in a separate image?

How can we render an object including his material name?

import bpy
from pathlib import Path

scene = bpy.context.scene
path = Path(scene.render.filepath)
suffix = ".png"

object = bpy.context.active_object
for index in range(len(object.material_slots)):
    src_string = format(index, "04d") + suffix
    src = path / src_string
    dst_string = object.material_slots[index].material.name  + suffix
    dst = path / dst_string
    print(str(src), str(dst))
    src.rename(dst)

Answer 1

import bpy
from pathlib import Path

scene = bpy.context.scene
path = Path(scene.render.filepath)
suffix = ".png"

def rename_object_render(object):
    for index in range(len(object.material_slots)):
        src_string = object.name + '_' + format(index+1, "04d") + suffix
        src = path / src_string
        dst_string = object.name + '_' + object.material_slots[index].material.name  + suffix
        dst = path / dst_string
        print(str(src), str(dst))
        src.rename(dst)

for object in bpy.context.selected_objects:
    rename_object_render(object)

I've made three important changes from the original script.

1. I've made the for loop into a function, since it will be invoked many times and it makes the code easier to read

2. I've added a loop to loop over all of the selected objects. If you want all objects instead, use bpy.data.objects in the for loop rather than bpy.context.selected_objects

3. I've changed src_string and dst_string assignments to prepend the object name.

I've also made one small change to fix a bug in the original script, replacing index by index+1 where relevant.

Answer 2

If you have two lists, one of every object with a unique material on it, and one with the image that needs to be renamed, I think using zip would be a better way to go about this. You already have the images rendered, so you don't need to get the scene render filepath, the images already have their filepath.

This isn't tested, you might need to work it a little bit but something like:

from pathlib import Path

objects = bpy.context.selectable_objects
frame_dir = Path('dir/to/rendered/png_images/')
# convert all a generator of all frames in the /render directory into a list
frames = list(frame_dir.iterdir())

# zip allows us to "zip" together two lists and iterate over them at the same # time. 
# example:
# a = [1,2,3]
# b = [x,y,z]

# for num, letter in zip(a, b):
#    print(num, letter)
# >>> 1 x
# >>> 2 y
# >>> 3 z

# enumerate is a way to get the index for free while inside a for loop

# example:
## for i, num, letter in enumerate(zip(a, b)):
#    print(i, num, letter)
# >>> 0 1 x
# >>> 1 2 y
# >>> 2 3 z

# put it all together and this is what we got
for i, frame, obj in enumerate(zip(objects, frames)):
    obj_name = obj.name
    # this is the material name that you want correct?
    material = obj.material_slots[0].name
    # string utility function to make suffixes like '0001, 0002' etc
    number = str(i).zfill(4)
    # use an f-string to format the new name of the image
    image_name = f"{material_name}_{number}.png"
    # the frame is a Path object we can rename easily
    frame.rename(image_name)

Again, you might need to check this for syntax errors or something, i didn't test it but I think it will do the trick for the most part.